In order to increase the strength and rigidity of sheet materials, corrugations are often formed in the material. This is often the case with aircraft skin panels wherein the interior surface of the panels has integrally formed corrugations for achieving requisite stiffness and strength.
In recent years, increasing use has been made of composite resin-impregnated fabrics, including graphite, Kevlar and glass fibers to achieve requisite panel strength at reduced weights and radar. In order to form such composite panels, a number of resin-impregnated sheets, constituting a base layer, are positioned over a mold form. Cores are then positioned on top of the base layer, and subsequently, an overlying layer of composite sheets is positioned over the core. The entire assembly is loaded into an autoclave where heat and pressure are applied to cause curing of the resin in the composite material and achieve superior bonding between the various sheets of the overlying layer and base layer. A principal disadvantage of the prior art lies in the use of cores which stick to the composite sheets after curing. As a result, their attempted removal may weaken or destroy the formed layers.
The present invention avoids this problem by utilizing cores fabricated from memory alloys.